Because of their widely ranging mechanical properties and their ability to be relatively easily machined and formed, plastic foams and elastomers have found wide use in a multitude of industrial and consumer applications. In particular, urethane materials, such as foams and elastomers, have been found to be well suited for many applications. Automobiles, for instance, contain a number of components, such as cabin interior parts, that are comprised of urethane foams and elastomers. Urethane foams are also used as carpet backing. Such urethane foams are typically categorized as flexible, semi-rigid, or rigid foams with flexible foams generally being softer, less dense, more pliable, and more subject to structural rebound subsequent to loading than rigid foams.
The production of urethane foams and elastomers are well known in the art. Urethanes are formed when isocyanate (NCO) groups react with hydroxyl (OH) groups. The most common method of urethane production is via the reaction of a polyol and a diisocyanate, which forms the backbone urethane group. A cross-linking agent and/or chain extender may also be added. Depending on the desired qualities of the final urethane product, the precise formulation may be varied. Variables in the formulation include the type and amounts of each of the reactants and additives.
In the case of a urethane foam, a blowing agent is added to cause gas or vapor to be evolved during the reaction. The blowing agent is one element that assists in creating the size of the void cells in the final foam, and commonly is a solvent with a relatively low boiling point or water. A low boiling solvent evaporates as heat is produced during the exothermic isocyanate/polyol reaction to form vapor bubbles. If water is used as a blowing agent, a reaction occurs between the water and the isocyanate group to form an amine and carbon dioxide (CO2) gas in the form of bubbles. In either case, as the reaction proceeds and the material solidifies, the vapor or gas bubbles are locked into place to form void cells. Final urethane foam density and rigidity may be controlled by varying the amount or type of blowing agent used.
A cross-linking agent is often used to promote chemical cross-linking to result in a structured final urethane product. The particular type and amount of cross-linking agent used will determine final urethane properties such as elongation, tensile strength, tightness of cell structure, tear resistance, and hardness. Generally, the degree of cross-linking that occurs correlates to the flexibility of the final foam product. Relatively low molecular weight compounds with greater than single functionality are found to be useful as cross-linking agents.
Catalysts may also be added to control reaction times and to effect final product qualities. The catalysts generally effect the speed of the reaction. In this respect, the catalyst interplays with the blowing agent to effect the final product density. Preferably, for foam urethane production, the reaction should proceed at a rate such that maximum gas or vapor evolution coincides with the hardening of the reaction mass. The catalyst may also effect the timing or speed of curing so that a urethane foam may be produced in a matter of minutes instead of hours.
Polyols currently used in the production of urethanes are petrochemicals being generally derived from propylene or ethylene oxides. Polyester polyols and polyether polyols are the most common polyols used in urethane production. For flexible foams, polyester or polyether polyols with molecular weights greater than 2,500 are generally used. For semi-rigid foams, polyester or polyether polyols with molecular weights of 2,000 to 6,000 are generally used, while for rigid foams, shorter chain polyols with molecular weights of 200 to 4,000 are generally used. There is a very wide variety of polyester and polyether polyols available for use, with particular polyols being used to engineer and produce a particular urethane elastomer or foam having desired particular final toughness, durability, density, flexibility, compression set ratios and modulus, and hardness qualities. Generally, higher molecular weight polyols and lower functionality polyols tend to produce more flexible foams than do lower molecular weight polyols and higher functionality polyols. In order to eliminate the need to produce, store, and use different polyols, it would be advantageous to have a single, versatile, renewable component that was capable of being used to create final urethane foams of widely varying qualities.
Currently, one method employed to increase the reactivity of petroleum based polyols includes propoxylation or ethoxylation. When propoxylation or ethoxylation is done on conventional petroleum based polyols, current industry practice is to employ about 70% propylene oxide by weight of the total weight of the polyol and propylene oxide to complete the reaction. Due to the large amount of alkyloxide typically used, the reaction if the alkyloxide and the petroleum based polyol is extremely exothermic and alkyloxides can be very expensive to use, especially in such high volumes. The exothermic nature of the reaction requires numerous safety precautions be undertaken when the process is conducted on an industrial scale.
Use of petrochemicals such as, polyester or polyether polyols is disadvantageous for a variety of reasons. As petrochemicals are ultimately derived from petroleum, they are a non-renewable resource. The production of a polyol requires a great deal of energy, as oil must be drilled, extracted from the ground, transported to refineries, refined, and otherwise processed to yield the polyol. These required efforts add to the cost of polyols and to the disadvantageous environmental effects of its production. Also, the price of polyols tends to be somewhat unpredictable. Their price tends to fluctuate based on the fluctuating price of petroleum.
Also, as the consuming public becomes more aware of environmental issues, there are distinct marketing disadvantages to petrochemical based products. Consumer demand for “greener” “bio-based” products continues to grow. The term “bio-based” or “greener” polyols for the purpose of this application is meant to be broadly interpreted to mean all polyols not derived exclusively from non-renewable resources. Petroleum and bio-based copolymers are also encompassed by the term “bio-based.” As a result, it would be most advantageous to replace polyester or polyether polyols, as used in the production of urethane elastomers and foams, with more versatile, renewable, less costly, and more environmentally friendly components.
The difficulties in the past that occurred due to the use of vegetable oil as the polyols to produce a urethane product include the inability to regulate the functionality of the polyol resulting in variations in urethane product where the industry demands relatively strict specifications be met and the fact that urethane products, in the past, outperformed vegetable oil based products in quality tests, such as carpet backing pull tests.
An unresolved need therefore exists for an improved functionality, vegetable oil based polyol of increased and selectable functionality for use in manufacturing a urethane materials such as, elastomers and foams. Also needed is a method of producing such urethane materials using the improved functionality, vegetable oil based polyol based on a reaction between isocyanates alone or as a prepolymer, in combination with the improved functionality polyol or a blend of the improved functionality polyol and other polyols including petrochemical based polyols. The products and methods of the present invention are particularly desirable because they relate to relatively inexpensive, versatile, renewable, environmentally friendly materials such as, vegetable oil, more particularly blown soy oil, transesterified with a saccharide, polysaccharide, or a sugar alcohol to form a polyol of increased and selectable functionality that can be a replacement for soy or petroleum based polyether or polyester polyols typically employed.